An explosion at a fireworks factory south east of Rome has killed six people, the latest of several blasts at factories that provide entertainment for Italy's religious and cultural festivals.

Witnesses told RAI state television they heard at least three thundering blasts, followed by flames that torched trees and shrubs around the rural area in Arpino, in the region of Latium, about 115 kilometres south east of Rome.

Hours after helicopters dropped water to douse the blaze, smoke smouldered through the hilly region as firefighters combed through the wreckage to determine if there were any other victims.

Frosinone province police spokeswoman Stefania Marazzo said six people had been killed in the blast, the cause of which was under investigation.

She confirmed that a similar blast in the area in 1994 killed six other people, but she could not immediately confirm a report on RAI that the 1994 blast occurred at a factory affiliated with the same family that owned the factory that exploded on Monday.

It was the latest in a number of similar accidents at Italian fireworks factories over the years.

Fireworks displays are very popular during religious and cultural celebrations, which are a fixture of Italian towns, particularly in the south.

In 2004, a factory near Naples blew up, killing five people. Another one near Naples in 2002 killed at least three people, while in 1996, a fireworks factory blast killed three people in Bari.

Some opposition lawmakers chalked the latest blast up to yet another case of unsafe workplaces in Italy and demanded greater safety measures and sanctions for violations. Labour minister Maurizio Sacconi said ministry investigators were already at the scene.

Calls for workplace safety are routine whenever there are on-the-job deaths in Italy. Experts say workplace safety enforcement is often lax in Italy.